The Journal of Nutrition Methodology and Mathematical Modeling Estimating the Population Distribution of Usual 24-Hour Sodium Excretion from Timed Urine Void Specimens Using a Statistical Approach

Background: High US sodium intake and national reduction efforts necessitate developing a feasible and valid monitoring method across the distribution of low-to-high sodium intake. Objective: We examined a statistical approach using timed urine voids to estimate the population distribution of usual 24-h sodium excretion. Methods: A sample of 407 adults, aged 18–39 y (54 % female, 48 % black), collected each void in a separate container for 24 h; 133 repeated the procedure 4–11 d later. Four timed voids (morning, afternoon, evening, overnight) were selected from each 24-h collection. We developed gender-specific equations to calibrate total sodium excreted in each of the one-void (e.g., morning) and combined two-void (e.g., morning + afternoon) urines to 24-h sodium excretion. The calibrated sodium excretionswere used to estimate the population distribution of usual 24-h sodium excretion. Participantswere then randomly assigned to modeling (n = 160) or validation (n = 247) groups to examine the bias in estimated population percentiles. Results:Median bias in predicting selected percentiles (5th, 25th, 50th, 75th, 95th) of usual 24-h sodium excretion with one-void urines ranged from 2367 to 284 mg (27.7 to 12.2 % of the observed usual excretions) for men and 2604 to 486 mg (214.6 to 23.7%) for women, and with two-void urines from2338 to 263mg (26.9 to 10.4%) and2166 to 153 mg (24.1 t